Week 6- Disease Spread By Rodents Flashcards
What are the old world arena viruses?
Lassa virus, lymphocytic choriomeningitis virus, and Lujo virus
What vector is responsible for the transmission of New World arenaviruses?
Sigmodontine rodents (new world mice and rats)
Name the New World arenaviruses.
Junin virus, Guanarito virus, Machupo virus, Sabia virus, Whitewater Arroyo virus, Chapare virus
What disease does Junin virus cause?
Argentine Hemorrhagic Fever
What disease does Guanarito virus cause?
Venezuelan Hemorrhagic Fever
What disease does Machupo virus cause?
Bolivian Hemorrhagic Fever
What disease does Sabia virus cause?
Brazilian Hemorrhagic Fever
What is the only New World, pathogenic, arenavirus found in North America?
Whitewater Arroyo Virus
How are arenaviruses transmitted?
- Inhalation of rodent excreta (urine, feces, saliva)
- Ingestion
- direct penetration (contact w/ contaminated materials, abrasions in skin)
- limited human-human transmission (Machupo virus only)
What are the symptoms of hemorrhagic fever caused by arenaviruses?
- fever, sore throat, myalgia, headache, anorexia, vomiting, petechial rash, thrombocytopenia, neutropenia, hemorrhaging in many organs (especially liver), pneumonia, neurological symptoms
- up to 35% mortality
What is the incubation period for arenaviruses? How long does illness usually last?
incubation- 7 to 14 days
illness- 10 to 14 days
Who is most affected by Argentine Hemorrhagic Fever?
agricultural workers in east/central Argentina, men
When is Argentine Hemorrhagic Fever most common?
- highest rate of infection during corn harvest season
- during harvest and plowing rodent excreta gets stirred up into dust
What factors are associated with the original outbreak of Bolivian Hemorrhagic Fever?
deforestation and the introduction of agriculture (corn)
What factors are associated with the emergence of Venezuelan Hemorrhagic Fever?
- deforestation in favor of agriculture and ranching
- forest rodents replaced by grassland rodents
Does Whitewater Arroyo virus infect humans often?
no, human infections are rare
Where is Whitewater Arroyo virus found?
rodents populations in Colorado, New Mexico, Texas, Oklahoma, Utah, and Southern California (up to 42% of the population in some areas)
What is the history of arenaviruses?
Relatively newly discovered viruses; Argentine HF (1955), Bolivian HF (1959), Whitewater Arroyo Virus (1999), Chapare Virus (2008)
What was the progression of arenaviruses cases in Bolivian HF?
- 100’s of cases in 1960s
- no cases between 1976 and 1993
- outbreak in 1994
- sporadic cases since then
- 200 cases in 2008
How are arenaviruses diagnosed?
- primarily through antibody based tests
- RT-PCR assays
- virus isolation
How are arenaviruses treated?
- ribavarin
- antibodies (convalescent plasma, whole blood, or immunoglobin)
- treatments are not effective against old world viruses
How can arenavirus infections be prevented?
- rodent control
- barrier protection for health care workers
- live attenuated virus (for Junin virus, cross-protective for Machupo, but not Guanarito)
What are hantaviruses?
Viruses of rodents (generally don’t cause disease), existed for about 30 million years, likely to be many more species
What diseases are caused by hantaviruses?
Hemorrhagic Fever with Renal Syndrome (HFRS) and Hantavirus Pulmonary Syndrome (HPS)
What viruses cause HFRS?
Korean HF, Hantaan virus (Asia, Europe), Dobrava virus (Balkans), Puumala virus, Seoul virus
(HFRS= Hemorrhagic Fever with Renal Syndrome)
What are the symptoms of HFRS?
abrupt onset of fever, severe abdominal or low back pain, nausea, hemorrhage, low BP, vascular leakage, kidney failure, shock
(HFRS= Hemorrhagic Fever with Renal Syndrome)
What viruses cause HPS?
-several viruses across Americas
-Sin Nombre (N. America)
-Andes virus (S. America)
(HPS= Hemorrhagic Pulmonary Syndrome)
What are the symptoms of HPS?
-fever, chills, myalgia, malaise, dizziness, leakage of fluid into alveoli, hypoxia, tachypnea, tachycardia
->50% mortality in initial outbreaks
(HPS= Hemorrhagic Pulmonary Syndrome)
What is the history of HFRS?
first identified in outbreak during Korean War (1951)
HFRS= Hemorrhagic Fever with Renal Syndrome
What is the history of HPS?
-first identified in 1993
-outbreak in 4 Corners region of US
-identification of hantavirus as cause led to development of diagnostis
-many hantaviruses discovered as a result
-<600 cases in the US
-outbreak occured in Yosemite National Park (2012)
(HPS= Hemorrhagic Pulmonary Syndrome)
What rodent is responsible for spreading Sin Nombre Virus?
Deer mouse (specific rodent transmits each disease)
How are rodents infected with hantaviruses?
Direct penetration (fighting, grooming) or inhalation (aerosolized excreta); chronic (life-long) infection; often no clinical signs
How are humans infected with hantaviruses?
Inhalation of aerosolized excreta
How is seasonality related to the spread of hantaviruses?
Transmission peaks during spring/summer
What are the risk factors for hantaviruses?
- Rural areas, higher number of rodents, cleaning rodent excreta
- In US, no known transmission between people, but is suspected in some cases of Andes virus
What is the immune response for hantaviruses?
- cells not directly damaged by infected cells
- mediators of immune response likely responsible for disease
- CD8+ T-cells kill infected cells, induce vascular leakage
- CD4+ T-cells secrete interferon gamma, activates macrophages, release additional cytokines, inflammatory response in lungs
What is the treatment for hantaviruses?
Supportive care; maintaining fluid balance, management of hypoxia, treatment of shock
How is hantavirus infection prevented?
no vaccine, education on safely cleaning up rodent excreta, rodent control in homes
What factors are associated with the emergence of AHF viruses and hantaviruses?
transport of rodents, climate, habitat disturbance, and community diversity
How do short term oscillations affect rodent populations?
- mild winters: high over-winter survival, reproduction throughout winter season, high numbers at the beginning of spring reproductive season
- high amounts of summer rainfall: keeps vegetation green longer, high rodent population throughout summer
What are the possible effects of long term climate changes on rodent populations?
- persistence of virus outside host depends on humidity and temperature (could alter dynamics of human infections and alter prevalence of infection in rodents)
- effect may depend of whether population is limited by competition or predation (may not affect population limited by predation, likely to affect one limited by food availability)
How might warm winters affect transmission of AHF and hantaviruses?
human behavior could be affected in a way that increases likelihood of infection
What could happen to AHF and hantarviruses if existing rodents are replaced by others that are better adapted?
Could alter how disease is transmitted- If SW US becomes hotter and drier, deer mouse will be transmitted by kangaroo rats who aren’t known to carry hantavirus
How does habitat disturbance affect the emergence of AHF and hantaviruses?
deforestation, agriculture, development, etc. lead to specialist rodent species becoming extinct, generalist species taking over (more likely to spread disease)
Why are hantaviruses and AHF viruses associated with generalist rodent species?
Specialist species have just as many viruses, but humans are less likely to come in contact; generalist species are more likely to be infected (larger ranger, high population density)
How does community diversity affect the emergence of AHF and hantaviruses?
Dilution effect, greater community diversity means less opportunities for transmission between suitable hosts
